Engineering of a minimal SaCas9 CRISPR/Cas system for gene editing and transcriptional regulation optimized by enhanced guide RNA

摘要

The presently claimed invention offers programmable and precise regulation of Cas9 functions by utilizing a set of compact Cas9 derivatives created by deleting conserved HNH and/or REC-C domains based on the structural information across variant class 2 CRISPR effectors. In addition, a novel strategy for engineering the dimeric gRNA-guided nuclease by splitting the mini-dSaCas9 and fusing the FokI domain right after the split point is claimed to increase the on-target DNA cleavage efficiency and potentially reduce the off-target effect because of a closer proximity of dimeric FokI nuclease to the target sequence. By combining the optimized and compact gRNA expression cassette and the downsized SaCas9 derivatives, the entire CRISPR/Cas system with different effector domains for transactivation, DNA cleavage and base editing is loaded into a single AAV virus. Such an all-in-one AAV-CRISPR/Cas9 system will be particularly appealing in biomedical applications that require safe and efficient delivery in vivo.